[lldb-dev] [Bug 17226] frame info lost after failed expression evaluation

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Nov 13 12:36:03 PST 2013


emaste at freebsd.org changed:

           What    |Removed                     |Added
           Assignee|lldb-dev at cs.uiuc.edu        |emaste at freebsd.org

--- Comment #3 from emaste at freebsd.org ---
It turns out this happens because FreeBSD does not allow user processes to
change PSL_RF via ptrace().  It seems the sequence of events is

1) breakpoint or exception
2) lldb checkpoints thread state - ptrace(..., PT_GETREGS) returns rflags with
PSL_RF set
3) expression is JITted and executed, leaving PSL_RF cleared in kernel thread
4) lldb tries to restore checkpointed thread state via PT_SETREGS
5) ptrace() returns EINVAL due to attempt to change PSL_RF

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